1. Field of the Invention
This invention relates to orthopedic surgical tools, and more particularly, to a patellar alignment and cutting guide for use in total knee arthroplasty.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98.
The surgical techniques of total knee arthroplasty, including patellofemoral articulation are well known in the art. The leading cause of clinical failure of total knee arthroplasty, or total knee revision, is patella problems such as pain and dysfunction of the patella femoral joint. Many patellar failures are related to patellar misalignment with the femoral and tibial replacement components and with the knee extensor mechanism. When the patella fails, it frequently cannot be so satisfactorily resurfaced, leading to either removal of its components or a patellectomy. These procedures often result in a major compromise to the functioning of the knee.
Another factor in determining ultimate patellar tracking and prosthesis longevity is accurate placement of the patellar prosthesis in the knee. Its articulation with the femoral groove and femoral component is especially integral to the longevity and success of the prosthesis. In order to maintain an acceptable overall patellar thickness and depth in the femoral groove, appropriate bone removal is a necessity, as well as accurate alignment of the cut bone surface and the patellar component in the sagittal, coronal and transverse planes.
One method popularized as a way to increase patellar prosthesis longevity is lateral retinacular release. Lateral retinacular release is used to improve patella tracking when the prosthesis does not track properly after it has been surgically applied. However, several problems associated with lateral release are well known including increased post-operative hemarthrosis and hematoma, Extensive lateral release also increases the probability of a vascular necrosis due to the sacrifice of the patellar branch of the superior lateral geniculate artery.
For a review of the surgical considerations regarding preparation of the to patellar component in total knee arthroplasty, refer to Patellar Component in Total Knee Arthroplasty, Kelly, Current Concepts in Primary and Revision Total Knee Arthroplasty, 1996, pages 153-158. Related articles describing the state of the art include the following references: Bone Scanning in the Assessment of Patellar Viability Following Knee Replacement, Wetzner, et al, Clinical Orthopedics and Related Research, Number 199, October 1985, pages 215-219; Technical Considerations in Total Knee Arthroplasty Dorr and Boiardo, Clinical Orthopedics and Related Research, Number 205, April 1986, pages 5-11; The Patellofemoral Component of Total Knee Arthroplasty, Brick and Scott, Clinical Orthopedics and Related Research, Number 231, June 1988, pages 163-178; Patellofemoral Functional Results and Complications With the Posterior Stabilized Total Condylar Knee Prosthesis, Aglietti et al, The Journal of Arthroplasty, Vol. 3, No. 1, March 1988, pages 17-25; Blood Supply to the Patella, Brick & Scott, The Journal of Arthroplasty, 1989 Supplement, pages S75-S79; Patellofemoral Complications Following Total Knee Arthroplasty, Ritter, et al, The Journal of Arthroplasty, Vol 11, No. 4, 1996, pages 368-372; A Soft Tissue Closure to Minimize Lateral Patellar Subluxation Following Total Knee Arthroplasty, Shaw, American Journal of Knee Surgery, April 1986, Vol. 1, No. 2; and Surgical Techniques and Instrumentation in Total Knee Arthroplasty, James Insall, Surgery of the Knee, 2.sup.nd. Ed., Vol. 2, Chapter 26, pages 767-772.
The success of surgical techniques in total knee arthroplasty and patellar longevity is also influenced by the tools available to the surgeon. Presently, suitable instrumentation systems and cutting guides for the tibial and femoral components are known in the art. For example, see Surgical Techniques and Instrumentation in Total Knee Arthroplasty, Chapter 26, pages 767-772. These systems and tools have improved surgeons abilities to implant the components properly and have reduced failures due to improper tibial and femoral condyle component alignment.
There are no known prior art teachings, however, of methods or tools which take into consideration the position of the patella in relation to the femoral condyle at the time of initial patella osteotomy. These cuts are extremely crucial in making sure that the proper relationship of the patella to the femoral groove is maintained and the patellar prosthetic is correctly sited. Instead, known methods and surgical tools for resection of the patella and resurfacing its posterior surface require extension of the knee and eversion of the patella from its anatomically correct position.
References which discuss subject matter related to patella resection include U.S. Pat. Nos. 5,542,947; 5,520,692; 5,380,332; 5,147,365; 5,129,908; 5,108,401; 5,021,055; and 4,633,862, incorporated herein by reference. Use of the alignment guides, clamps, and surgical saws disclosed in these prior art references for removal of the diseased patellar joint surface and for creating the interface for the patellar component are used with the knee extended, the patella everted, and the extensor and connecting tissue pulled away, so the posterior surface of the patella is exposed. Although the aforementioned references disclose how a surgeon typically retracts, reshapes, and profiles the patella, these procedures limit a surgeon's ability to accurately align the patellar component in reference to either the femoral or tibial component. There is no teaching, discussion or disclosure of resurfacing a patella in situ, taking advantage of the anatomic position of the patella with relation to the femoral condyle.
Referring to FIGS. 20 and 21, examples of a femoral component 150 depicting anatomically correct positions of the patella in relation to the femoral articulating surfaces are shown. In FIG. 20, the patella 160 is shown adjacent to the femoral condyle 152 where it articulates with portions of the femoral condyle in the true femorotibial area when the knee is in full flexion. When the knee is in extension, the patella 160 articulates solely with the femoropatellar gliding surface 156 as shown in FIG. 21.
When the patella is everted to make the resurfacing cuts, accurate alignment of the patellar surface with the extensor mechanism and articulating surfaces is inordinately difficult. Therefore, there remains a need for a method of accurate alignment, resurfacing of the patella, and implantation of the patellar component relative to the femoral and tibial components and tools for achieving the same. Such a method and tools would decrease the failures of total knee arthroplasty due to problems with the patellar femoral joint, misalignment with the knee extensor mechanism, and polyethylene wear, thereby improving patellar tracking and increasing prosthesis longevity. The present invention meets these needs.